THE INFLUENCE OF LANDSCAPE POSITION ON LAKE CHEMICAL RESPONSES TO DROUGHT IN NORTHERN WISCONSIN

Climatic shifts to drier conditions during drought alter the hydrologi c pathways of water and solute flow to aquatic ecosystems. We examined differences in drought-induced trends in the semiconservative cations , Ca+Mg, in seven northern Wisconsin lakes. These spanned the range of hydrologic settings in the region, including hydraulically mounded, g roundwater flowthrough, and groundwater-discharge lakes. Parallel incr eases in concentration across the seven lakes during drought were attr ibutable to evapoconcentration. However, we observed divergent trends for mass, which better reflects altered solute flux by accounting for changes in lake volume. Ca+Mg mass increased in three groundwater-domi nated lakes as precipitation inputs were low and groundwater dischargi ng from longer flowpaths became proportionately more important. In con trast, decreases in Ca+Mg mass for two precipitation-dominated lakes r eflected diminished inputs of solute-rich groundwater. Landscape posit ion, defined by the spatial position of a lake within a hydrologic flo w system, accounted for the divergence in chemical responses to drough t.